Lipids have multiple industrial applications, including in the cosmetic and food industries, as well as serving as precursors for biodiesel and biochemical production. Microbial lipids are produced by many oleaginous organisms, including the well-characterized yeast Yarrowia lipolytica. Lipid yield in oleaginous organisms can be increased by up-regulation or down-regulation or deletion of genes implicated in the lipid pathway. For example, it was reported that up-regulation of native Y. lipolytica DGA1 significantly increased lipid yield and productivity (Metabolic Engineering 15:1-9 (2013)).
Y. lipolytica DGA1 is a type 2 diacylglycerol acyltransferase encoded by the Y. lipolytica diacylglycerol acyltransferase gene DGAT2. DGA1 is one of the key enzymes in the lipid pathway, and it is involved in the final step of triacylglycerol (TAG) synthesis. Triacylglycerols are the major form of storage lipids in Y. lipolytica. Recent data suggests that DGA1 efficiency may be a significant factor for high levels of lipid accumulation in oleaginous organisms (Metabolic Engineering 15:1-9 (2013)). Additionally, DGA1 genes from other species can be introduced into the host genome and have a significant effect on lipid production and composition. For example, other oleaginous yeast, such as Rhodosporidium toruloides and Lipomyces starkeyi, are able to accumulate significantly more lipids compared to wild type Y. lipolytica strains. It was demonstrated that overexpression in Y. lipolytica of DGA1 from organisms with higher native lipid production levels had a greater effect on Y. lipolytica lipid production than overexpression of native Y. lipolytica DGA1 (U.S. Ser. No. 61/943,664; incorporated by reference). Despite efforts to increase lipid yield in Y. lipolytica by overexpression of DGA1 from Mortierella alpine, no significant effect on lipid production levels has been reported (U.S. Pat. No. 7,198,937; incorporated by reference).
The deletion of genes involved in the breakdown of lipids or in pathways that draw flux away from lipid biosynthesis has also been studied. Dulermo et al. demonstrated that the deletion of the triacylglycerol lipase gene TGL3 nearly doubled the total lipid content accumulated by Y. lipolytica (Biochimica Biophysica Acta 1831:1486-95 (2013)). The TGL3 protein is one of two intracellular lipases responsible for the first step of triacylglyccrol degradation in Y. lipolytica. 